Combining chemotherapy with an immune-blocking drug could stop cancer recurrence

Giving patients a drug that blocks part of the immune system from going into overdrive might help prevent cancer coming back in some people, according to research published in Cancer Research (2015; doi:10.1158/0008-5472.CAN-14-3587).

Scientists from the University of Sheffield in the United Kingdom who were funded by Cancer Research UK found that the cancer-killing action of chemotherapy can trigger a swarm of wound-healing white blood cells to cluster around blood vessels in a treatment-hit tumor. These cells, called M2 macrophages, repair tissue damage and build new blood vessels. This process sometimes helps the tumor to grow again after treatment.

However, by treating mice with cancer with the drug plerixafor, which stops these macrophages from working, the researchers markedly reduced the speed at which tumors grew back after chemotherapy.

"Scientists already knew that the body's drive to heal itself can sometimes backfire when the immune system reacts to tissue damage. Our research shows that treating tumors with chemotherapy can activate this part of the immune system, and this then helps tumors re-grow afterwards,” said lead scientist Professor Claire Lewis, DPhil, DSc, of the University of Sheffield's Department of Oncology.

"But combining chemotherapy with a drug that switches off this part of the body's repair system slowed the growth of tumors after chemotherapy. This could be particularly important for patients who can't have surgery and, therefore, need chemotherapy to help them live for as long as possible."

Clinical trials of patients are needed to confirm these early findings to see if the drug, which is already used in patients for other reasons, such as bone marrow transplants, could help cancer patients after chemotherapy.

“We don't understand all the reasons why tumors do come back, but this study sheds new light on the role of the immune system in causing tumors to grow again and, importantly, identifies a drug that could block this happening if given at the same time as chemotherapy.

McCarthy added that this is early research carried out in mice. More work will be needed to see if blocking M2 macrophages can also slow down tumor re-growth in patients.